Inspecting apparatus using fiber optics



5 Sheets-Sheet l Hwwig@ INSPECTING APPARATUS UsNG FIBER OPTICS urli( 9S.a.

St d? Am@ QR, @n S JI 2 mmukmm Henn. A u. QN

...RR 2 NS Q ew Q 0L www Il m 0 X w alf A on 1 June 27, 1967 E. E.SHELDON INSPECTING APPARATUS USING FIBER OPTICS Original Filed March 1l,1954 5 Sheetsheet Ournn .Sunni 5 mnru im 0u nur 511mm i P/rkuP fadE MINVENTOR.

[www [mm/L ./luom bef/MM .lume 27, 1967 E. E. sHELDoN 3,328,594

INSPECTING APPARATUS USING FIBER OPTICS Original Filed March ll, 1954 3Sheets-Sheet E ff #fw L, n3

I/ l l l 51mm' lia;

lf YE f 3 24 f C5416 hun:

l 55 kfaQ/5,14

i INVENTOR.

.Em/mo fom/ufl. Suena United States Patent O 3,328,594 INSPECTlNGAPPARATUS USING FIBER OPTICS Edward E. Sheldon, 30 E. 40th St.,

New York, NY. 10016 t Division or applications Jan. 27, 1965, Ser. No.423,433, and Feb. 2, 1962, Ser. No. 170,745, now Patent No. 3,205,390,dated Sept. 7, 1965', which in turn is a division of Ser. No. 785,894,Jan. 9, 1959, now Patent No. 3,027,477, dated Mar. 27, 1962, and Ser.No. 415,669, Mar. 11, 1954, now Patent No. 2,877,363, dated Mar. 10,1959. Divided and this application Nov. 26, 1965, Ser. No. 509,712

13 Claims. (Cl. Z50- 227) This invention relates to `a novel instrumentfor examination of the interior of the parts, channels or passages whichare inaccessible to the examiner and is a division of my co-pendingapplication Ser. No. 428,483, tiled Jan. 27, 1965, and is a division ofmy Patent No. 3,205,390 tiled Feb. 2, 1962, and issued Sept. 7, 1965which was copending and was a division of U.S. Patents 3,027,477

lcd on Jan. 9, 1959, and 2,877,368 led on Mar. 1l, 1954.

Due to the inability of light to pass around corners, the presentinstruments used for such examination have to be straight and rigid sothat the eye of the examiner and the examined part are in one straightline. The instruments using optical lenses or prisms will not help inthe situation when the shape and the size of the examined part isvariable and unknown in advance. 'In such a case, the position of thecurves and angulations in the examined parts or passages is unknown andtherefore the lenses or prisms cannot be positioned to anticipatedeviations of the axis of the examined channel from the straight line.

The purpose of this invention is to provide means for inspection ofinaccessible channels, such as hollow parts of machinery or of otherinaccessible tortuous passages. My device may be introduced inside of apart which cannot be inspected visually without dismantling ordestroying the whole machine and will transmit the image of said part tothe observer outside of said part. My invention will be especiallyuseful for the examination of coils and pipes or other curvedstructures. My device can be also used as a probe to be inserted into asolid object and to transmit information about its internal structure.

Another objective of my invention is to intensify the image of theexamined internal parts or passages so that the nal image will bepresented to the observer with the luminosity facilitating inspection ofsaid image.

Another purpose of my invention is to enable simultaneous observation ofsaid inaccessible parts by many examiners, situated in close or remotelocations, which was not possible until now.

Another objective of this invention is to change, decrease or amplifythe contrast of the image of the exa-mined part.

The objectives of my invention are realized by a novel device which isflexible to allow its introduction into the examined part regardless ofits curvatures or angulations and which after its introduction into theexamined part will produce a light image of said part, will next convertsaid light image into video signals and will transmit said video signalsoutside of said part. Video signals are reconverted in receivers outsideof the examined part into visible images for inspection or recording. Myintrascopic device can produce black and white images, as well asmulticolor images, showing faithfully or arbitrarily the colors of theexamined part.

In particular this novel device makes use of a television pick-up tubeconsisting of two separate independent elements which can be introducedseparately into the examined part and which after introduction work inrice cooperation as a television camera. As each of these two separateelements is smaller in size than any conventional television camera canbe made, this novel television camera can be introduced into locationswhich, because of small size or tortuous shape of passages leading tothem, were inaccessible to the :most miniaturized television camerasknown in the art.

Another marked improvement in my novel television camera is eliminationof magnetic dellecting coils which are bulky and occupy so much spacethat even a small television tube using them cannot be introduced intonarrow passages. The use ot conventional electrostatic dei'lectingsystem results into a marked distortion of images especially in pick-uptubes using the slow scanning electron beam. These drawbacks areeliminated in my intrascope and therefore in spite of its very smallsize it is capable of producing images of good definition and contrast.

In some applications even this novel intrascope utilizing a pick-up tubedivided into two separate independent elements cannot be introduced intovery narrow or tortuous passages. In such cases I use a novel imageconductor in combination with my television pick-up tube. The novelimage conductor consists of `a liexible guide of material having a highindex of refraction and critical angle of reflection which prevents theescape of the light from said guide. The novel image conductor may bemade of any desired size or shape and therefore it can penetrate themost inaccessible locations and can transmit the image therefrom to thetelevision pick-up tube or directly to the outside to the observer.

In the drawings:

FIGURE l represents a partially sectioned view of the novel intrascope;

FIGURES la, 1b and lc show a modilication of the intrascope;

FGURE 1d shows a intrascope with a simplified television camera tube;

FIGURE 2 shows a combination of light image conductor with a televisionpick-up tube;

FlGURES 2a and 2b represent a modification of the combination comprisingan image conductor and a pick-up tube;

FlGURE 3 represents a modified embodiment of my intrascope provided withimage conductor;

FIGURE 3a represents a modification of my intrascope in which imageconductor is in contact with the distal end of the intrascope;

FIGURES 4 and 5 represent a simplilied intrascope provided with a lightimage conductor; and

FIGURE 6 represents an embodiment of my intrascope provided with animage amplifying tube.

The new device which may be called the intrascope 1 is shown in FIGUREl. The handle 2 is a hollow tube of diameter corresponding to theexamined part. The handle may be rigid or semi-flexible or completelytiexible according to the part to be examined. At the end of the handlebegins the flexible part 2a of the intrascope which also has width andlength suitable for the size of the examined part. In case theintrascope is used for examination of fragile parts, the part 2a must bevery liexiblc and pliable in order to avoid damage to the wall of theexamined part. The basic feature of the material for the ll'exible partof the intrascope is therefore that it must be easily bent and molded bythe walls of the passages ini which it is being introduced. Suchmaterial may be a suitt able plastic, or rubber 26 of the type used byDavol Rubi ber Company of Providence, Rl., for their gastric tubesa Incase the intrascope is used for investigation of sturdy," parts or ofmachinery the part 2a may be obviously more rigid. The liexible part 2aof the intrascope may bein such a case made of the stainless steelspiral sheet designed not only for durability but also to maintain theproper degree of flexibility and elasticity. The metal spiral is taperedto insure its uniform bending. The intrascope Imay be covered with anouter tubing 26a such as of neoprene. This prevents dust particles andmoisture from affecting the optical and pick-up system located inside ofthe intrascope. At the end of the flexible part there is a semi-flexibletip 3 which may be screwed on the flexible part and can be easilyremoved giving thereby access to the inner structures of the intrascope.The tip consists of a rubber conical nger and serves to facilitate thegliding of the intrascope within the examined part. In order tofacilitate the introduction of the intrascope into parts which have nocurves my device can be made semi-rigid by inserting into it asemi-rigid stilet. In case the intrascope is used as a probe forinsertion into a solid object the tip 3 should be preferably rigid andsharply pointed to be able to pierce the examined object.

In some cases the examined part has to be distended by air or fluidinsufilation prior to the examination. A special air pump attachment 44and a channel 44a in the intrascope is provided for this purpose. Thechannel 44a also may serve to evacuate contents of the examined partbefore examination to improve visibility. The knob 45 on the proximalend of the intrascope serves to indicate to the examiner the position ofwindows 12 and 18 of the intrascope. In some cases the layer 26 shouldbe of a dielectric material to prevent any short-circuits.

In the distal end of the flexible part of the intrascope there is ahousing box 5 containing the illumination system 7. The box 5 may alsobe attached to the inner walls of the intrascope by means of thebrackets or may be held by springs. It is obvious that there are manymeans for attachment of the box 5 which are well known in the art. Allwalls of the housing box 5 except the one facing the television pick-upt-ube 16 are provided with Windows 149 for transmission of the lightfrom the illuminating system 7. These Windows are correlated with thewindows 12 in the flexible part of the intrascope which transmit thelight from the illuminating system to lthe examined part. In some casesthe windows 12 may be made to extend over the circumference of theintrascope. In some cases the window to transmit illumination from lthelight source to the examined part may also be provided in the distal endof the intrascope instead of being in its side walls, and in such casethe tip may be made of transparent material or may be omitted. Windows12 may be provided with shutters which can be controlled from theproximal end of the intrascope which is outside of the examined part.

The illuminating system may consist of the electrical bulb 7. Theelectrical bulb may be mounted in the housing box S by means of a socket7a. In some cases it is advantageous to use the objective lens 11between the light bulb and window 12 in order to concentrate the lighton one field. The lens may be held in position by brackets 11a. Thelight bulb is activated by the source of electrical power 9 situatedoutside of the examined part. Such a source may be the commercialelectrical current or batte-ry of dry cells. The flexible electricalcable 8 leads from the socket '7a to said outside source of electricalcurrent 9. The cable is a lacquered, double insulated electric wire, iscovered in addition with liquid rubber and is vulcanized in order toprevent a short circuit. rl`he housing unit 5 may be in some casesomitted and the light source may be attached to the socket 7a which isheld by brackets.

In the flexible part 2a proximally to the housing box 5, there is arigid non-transparent housing compartment 14 containing the opticalsystem 1S and the novel television pick-up tubes 16a and 1612. Thehousing 14 has an opening 17 in which the optical system 15 is lodgedand which serves to admit the image of the examined part. This openingis correlated with windows 18 in the flexible part of the intrascopewhich transmit the image of the CTI examined part. In some cases thewindows 18 may be made to extend over all the circumference of theintrascope. rl`he windows 1? may be provided with shutters operated fromthe proximal end of the intrascope which is externally to the examinedpart. The housing 14 containing the television pick-up tubes 16a and 16hand the optical system may be attached to the inner Wall of the flexiblepart 2a of the intrascope by means of brackets or may be held by springs27a. As the housing box fits into the encasing holding member 26 and isheld by it tightly, in some cases no additional supporting means such assprings are necessary.

The optical system 1S may consist of 90 gable prism 2@ and of lens 21.The optical system may have its own housing unit instead of being lodgedin the compartment 14 and may be then introduced into the intrascopeseparately.

In some cases it is desirable to have a large field of vision and at thesame time to preserve the necessary magnification of the examined part.In such a case instead of the pris-m 2) a rotating mirror should beused. The mirror has a first surface coating which eliminates thereflections and is activated by 4the magnetic solenoid placed beneaththe mirror. The solenoid is connected by the elastic cable with thecontrols outside of the examined part and can tip the mirror from theretrograde position to the forward position giving thereby an additionalfield of vision without the necessity of moving the intrascope. Theimage of the examined part is reflected by the mirror on the objectivelens which focuses said image on the photocathode of the noveltelevision pick-up tube 16b described below. In case the magnificationof the examined part is not necessary a large field of vision can beobtained by using the lens providing field of vision instead of theusual 45-50. The image produced by the optical system is inverted but itcan be reverted to the original position either by an additional lens orelectronoptically in the viewing tube. The rotating mirror may alsoserve to admit image either through window 18 or 18a without rotatingthe whole camera 16.

The housing box 14 contains the novel miniature television camera 16which was designed to reduce to the minimum the size of the televisioncamera. The television pick-up tubes known previously in the art couldbe miniaturized only to a certain degree, which was not sufiicient incertain applications as some of the examined parts and too small toallow the introduction even of the smallest conventional pick-up tube.This is true especially for the type of tribes having externaldeflecting coils such as of magnetic or electromagnetic type, and insuch situations, my novel camera 16 will be very suitable as it does notrequire any external deflecting or focusing coils at all. The camera 16consists of two vacuum tubes 16a and 16b. The tube 16a has an electrongun 28 which produces an electron beam 29. The electron beam 29 isfocused by electrostatic field3tl. The electron-optical system forfocusing the electron beam 29 may be simplified and markedly reduced inlength by using the unipotential electrostatic lens instead of the usualtwo-'lens system. The electron beam 29 is deflected by electrostaticplates 30a and tlb in two perpendicular to each other planes. Theelectrostatic pilates are energized by signals from saw-tooth generators2 which are situated outside of the examined part. The generators 32 areconnected with electrostatic plates 30a and 301; by means of flexiblewires. One deflecting eld is produced by the horizontal deflectionplates 30a and may have line frequency such as 545,000 cycles persecond. Another deflecting field is provided by the vertical deflectionplates Sfb and may have field frequency such as 1.5-60 cycles persecond. In this way the electron beam 29 is made to scan the fluorescentscreen 31 in a regular television raster. The deflection system may befurther simplified and lminiaturized by having only horizontaldeflection plates 39a. The vertical deflections 30]? are eliminated andthe vertical deliection of the fluorescent light spot is provided by therotating drum 71 with plural mirrors 72 as shown in FIGURE ld. Thefluorescent screen 3l `may be provided with electron transparentmetallic conducting backing layer 31a such as of aluminum. Thefluorescent screen 3l must be of a phosphor of a very short persistencein order to obtain a good resolu tion of the image. Zn() has decay timeof 1 microseeond and is suitable for this purpose. Still better resultsmay be obtained by means of ZnS phosphor and using only the ultra-violetcomponent of its fluorescent emission which has a decay time of 1A()microsecond. ln some cases, it is preferable to make the fluorescentscreen 31 of semispherical curved shape as it will improve definition ofthe tiying light spot. The tluorescent layer 31 may also be deposited onthe supporting mesh screen instead of being deposited on the wall of thevacuum tube. This will improve definition of the flying light spot.

The vacu-um tube 16a operates in combination with the vacuum tube labforming together the novel television camera 16. The vacuum tube 1Gb hasa photoemissive electrode 33 which may be deposited or attached to oneof the walls of said vacuum tube. In some cases it is preferable toprovide a light transparent conducting layer 3311 such as of materialknown in the trade as Nesa, or of compounds of tin or of cadmium, on theside of said photoemissive electrode 33 facing the fluorescent screen31. The photoemissive electrode 33 may be of CsOAg or of caesium,lithium or rubidium on antimony, arsenic or bismuth. At the opposite endof the vacuum tube 1Gb there is provided photocathode 34 which consistsof a light transparent signal plate 34a, a light transparent insulatinglayer 34h and of a photoemissive mosaic 34C. The signal plate 34a may bea thin transparent layer of metal or other conducting material. Theinsulating layer Sab may be of mica, silica, or other transparentdielectric material and photoemissive mosaic 34C may be of CsOAg or ofcaesium, -rubidiurn or lithium on antimony, arsenic or bismuth. in somecases the photoemissive layer 34e may be instead of a mosaic, also ofcontinuous type. ln cases in which electrostatic focusing eld 23 is usedto focus the scanning electron beam 33a on the mosaic 3de, much betterresolution will be obtained by making such mosaic of a curvedsemispherical shape. In addition, the use of such spherically shapedphotocathode will eliminate instability of the image which is verymarked when using electrostatic fields for focusing a slow electronbeam.

The light image of the examined part is projected by the optical systemon the photocathode 3d of the vacuum tube 1611. The light image producesemission of photoelectrons from the layer 345e. As a result a positivecharge image having the pattern of said light image is left on thephotoemissive mosaic 34C. Both vacuum tubes 16a and 16b are held inapposition to each other and in such a manner that the liuorescentscreen 31 of the vacuum tube 16u is adjacent to the photoemissiveelectrode 33 of the tube 1611. The scanning electron beam 29 impingingon the fluorescent screen 31 produces a light spot at each point of itsimpingement. The scanning illumination excites the photoemissiveelectrode 33 and produces thereby a ne scanning beam of photoelectrons33a. The photo electron beam 33a is the scanning type because it isproduced by the scanning electron beam 29. The photoelectron beam 33amay be further focused by electrostatic fields 23. In some cases thephotoemissive electrode 33 and the mosaic 34 are disposed so close toeach other that the focusing fields may be eliminated which will furtherreduce the size of the vacuum tube 1611. When the focusing fields areomitted I found that separation of electrode 33 and mosaic 34 should notexceed 0.25 millimeter.

In a vacuum tube 16h instead of the photoemissive mosaic l may also usea photoconductive photocathode such as shown below in FIGURE 2b. Thephotoconductive photocathode comprises a conducting signal plate d 3dewhich is connected to the circuit producing video signals and aphotoconductive layer 34e deposited thereon as shown in FGURE 2b. Thephotoconductive layer may `e of selenium, zinc sclenide or of antimonysulfide or of other photoconducting materials.

Another important modication of the vacuum tube 16h was accomplished byeliminating the photoemissive electrode 33. In this embodiment ofinvention as shown in tube 75 in FGURE lc, the iluorescent light scansdirectly the photoemissive mosaic 34e. The emission of photoelectronsfrom the photoemissive mosaic 34C produces signals in the capacitativelycoupled signal plate fida. These signals are converted into videosignals in the manner well known in the art.

In the examination of stationary objects my intrascope may be furthersimplified by using as a source of scanning light instead of a vacuumtube 16a, a steady source of light such as an electrical bulb 74 incombination with an oscillating mirror 73 or rotating drum as shown inFIG. lc. The oscillating mirror or drum is limited in frequency ofoscillations therefore video signals produced by this device must bestored until the whole image is assembled. lt is also possible to useinstead of a storage tube for video signals, a receiver tube such as akinescope having a memory screen such as dark trace screen. Also afacsimile receiver can be used for this purpose. The pick'up tube 75 maybe also simplified by eliminating the electrode 33 as was explainedabove. The oscillating mirror may be mounted on a pivot and may beenergized by solenoids through which the current of high frequency isflowing. One set of coils serve to move the mirror in horizontal axis.Another set of coils is vibrating the mir ror on vertical axis. Theaction of both coils makes the `mirror oscillatc in such a manner thatthe light reflected by said mirror will scan the area on which it isprojected in the same manner as the [lying spot which is produced by acathode-ray tube. The construction of an oscillating mirror is wellknown in the art and it is believed therefore that its further detaileddescription will only serve to complicate the drawings.

The electron beam 33a may be of high velocity such as used in theiconoscope type ot television pick-up tubes or may be of a slowvelocity. ln this embodiment of my invention, I use the slow scanningelectron beam. It is to be understood however that the fast scanningelectron beam may be used in my invention as well. The electron beam 33ascanning across the charge image stored in the mosaic 34e converts saidimage into electrical signals which appear at the signal plate 34u.These electrical signals can be converted into video signals over theresistance in the manner well known in the art. The video signals aretransmitted by the liexible coaxial cable 43 from the intrascope withinthe examined part to the video amplifiers 43u outside of said part. Theamplified signals are transmitted from the amplifiers to the viewingtube of kinescope type 37 and are reconstructed therein into the visibleimage representing the image ot the examined part. The viewing tube maybe of kinescope type and does not have to be described in detail as itis well known in the art. The examined part will appear on thelluorescent screen 37u of the viewing tube where it can be inspected bymany examiners. Transmission of the image from the amplifier 3a to theviewing tube can be done by coaxial cable Li3 or by high frequencywaves. The image can be sent therefore not only to the immediate, butalso to the remote receivers or may be transmitted to multipleindependent viewing tubes for the benefit of many examiners which wasone of the objectives of this invention. The image on the viewing tube37 may also be photographed simultaneously with the intrascopeexamination in order to make a permanent record which was anotherpurpose of this invention.

The contrast of the reproduced image may be changed, diminished orincreased according to the needs of particular examination by usingamplifiers provided with variable mu tubes, or by the use of a4kineseope in which the gamma can be controlled. The signal to noiseratio of this system and therefore the definition of the reproducedimage may be improved by using in the amplifiers discriminating circuitswhich reject signals below the predetermined amplitude and eliminatetherefore most of the noise signals. The coaxial cable 43 within theexamined part may be encased in the above described means 26 or 26a forinserting the intrascope or may be attached to them.

The voltages for the operation of the tubes 16a and 16h are suppliedthrough the flexible elastic wires 8a from the source of the electricalpower 9 outside of the examined part. In the same way the horizontal andvertical synchronizing circuits, focusing fields and dciiecting circuitsare supplied with electrical energy from the outside source of power 9.The synchronizing and deflecting circuits and focussing fields are notdescribed in detail as they are well known in the art and it is believedthey would only complicate the drawings. In some cases the coaxial cable43 may be outside of said inserting means 26 or 26a.

The housing 14 containing the television camera can be rotated in itsposition in the intrascope `so that the optical system 15 can be made toface the window 18 or 18a and to see thereby various areas of thecircumference of the examined part. The rotation of the camera can beaccomplished by means of a pusher 15a which fits into extensions 10b ofthe box 14. The rotation of the camera may be preferable in some casesto the rotation of the whole intrascope which accomplishes the samepurpose.

The main rigid portion of the flexible intrascope is the televisioncamera 16. Therefore the shorter the television camera is, the easier itwill be for the intrascope to pass through sharply angulated or curvedpassages. One of the advantages of the novel pick-up tube 16 is that itmakes it possible to break up the smallest pickup tube into twocomponent parts such as tubes 16a and 16h and introduce each of saidtubes into the examined part separately, reducing thereby considerablythe rigid portion of the intrascope which is due to the televisioncamera, as shown in FIGURE 1a.

To accomplish these objectives the flexible intrascope 1a is introducedfirst into the examined part while containing only the box housing thelight source 7. Inside of the intrascope 1a, shown in FIGURE laproximally to the box 5 there is a ringslike partition which serves as astop 27 for the pick-up tube 16b which is to be introduced later. It isobvious that the shape of this stop may vary. The rest of the intrascope1a is empty. The intrascope 1a is introduced first into the examinedpart. As the only rigid part of the intrascope is now the box 5 which isvery small, this intrascope can easily pass even through very narrow andcurved passages. After the intrascope 1a has been introduced into theexamined part for a desired distance which can be read easily on themarkings provided on the outside wall of the intrascope, the next stepbegins. Now the housing box 14h in which the vacuum pick-up tube 16h ismounted is introduced into the intrascope. The housing box 14]] ispushed into the intrascope, until it reaches the stop 27. The box 14bmay be held against the stop 27 by spring extensions 27a, as shown inFIGURE l, on said stop 27. The housing box Mb may be pushed into itsposition by a exible elastic pusher 15a which is fitted into theproximal end of the housing box 14h. For this pupose the housing box14]) is provided with a ringlike extension a at its base which hasspring-like properties. rl`he head of the flexible pusher a ts into thisextension and is kept in position by it. The flexible pusher 15a mayalso be provided with electrical coils 6a at its distal end which isadjacent to the element to be introduced into the intrascope. The coils6a are connected to the source of electrical power situated outside ofthe examined part. In this way, the head of the pusher may be givenelectro-magnetic properties by closing the circuit, energizing saidcoils 6a. The pusher 15a will be held therefore in the elements to beintroduced into the intrascope, such as boxes 14a, Mb or the opticalsystem 15, not only by the mechanical pressure of the extensions lila,or 10b, but by magnetic attraction as well. When the pusher 15a is to bewithdrawn, the current supplying the coils 6a is shut 0H. To facilitatethe guiding of the box 14h into the intrascope, a set of threads 86, asshown in FIGURE 1b may be used which are at one end attached to the stop27, and which are threaded through the perforations in the extensions 87of the housing box 14h. After the box 14h has been introduced into itsproper position in the intrascope, the pusher 15a is removed. Anotherset of threads 89 is attached to the extensions 38 in the housing unit14b and serves to pull out said box 14h to the exterior of the examinedpart when the examination is nished. This arrangement is shown in FIGURE1b.

The housing box may be omitted in some cases and the tube 16h may beintroduced into the intrascope without any housing and will be held inposition by the same means as described above for holding the box 1417.

After the box 14b with the tube 1617 has been introduced, the box 14ahousing the tube 16a is introduced now into the intrascope in a similarmanner as was described above. Both boxes 14b and 14a have openings attheir proximal and distal ends respectively, which makes it possible tobring the fluorescent screen 31 of the tube 16a in close apposition tothe photoemissive electrode 33 in the tube 16]). The boxes 14a and 14bare provided with mechanical means for securing a good contact of theproximal end of the tube 1611 with the distal end of the tube 16a. Oneway of providing such a contact is to make the compartment 14a fitinside of the spring-like ange 27a at the proximal end of thecompartment 14h. The housing box 14a contains vacuum tube 16a which hasbeen described above. The housing box 14a is provided with spring-likeextensions 10b which serve to accommodate the head of the pusher 15a.

The housing box 14a is pushed into the intrascope until it reaches theposition of the stop 27b. The stop 27b is so situated that when thehousing box 14a reaches it the tubes 16h and 16a will be apposition toeach other. In some cases flexible coils which can be converted intomagnets by passing through them an alternating current from an outsidesource of electrical power may be provided on the stops 27 and 27b or atextensions 10a or 1Gb of the intrascope to help the positioning of boxes14a and 14h. In this way the rigid portion of the intrascope which hasto pass through a narrow passage or acute curvature is now only afraction of the rigid part of intrascopes which use even the 'smallestpick-up tube of conventional type. This represents an importantimprovement as it makes it possible to introduce the intrascope intoparts which were not accessible previously to examination.

It should be understood that all my intrascopes can serve for producingand transmitting color images as well. The color system may be ofmechanical type such as using a color wheel, or may be of electronictype, such as using an optical system to split the light image into itscomponent colors and to project them on television pickup system.

In some applications even my novel intrascopic device cannot beintroduced through the narrow or angulated passages. For such cases Idesigned a novel apparatus which will overcome even to 360 bends inpassages. FIG- URE 2 shows this embodiment of my invention. Theintrascope 50 is provided with a novel image conductor 51. The imageconductor 51 consists of multiple fibers of maasaasea terial having ahigh refractive index such as quartz, rutile or special plastics. Inmany applications the image conductor must be exible and easilymalleable. In such cases acrylic plastics such as Lucite or polystyrenemay be used. Especially Lucite is suitable for this purpose because itcauses smaller losses of conducted light than other materials. Luciteand other above mentioned materials characterized by a high refractiveindex have the property of internal reliection of the light conducted bythem. Such materials cannot conduct a whole image as such but they canconduct well a light signal. The size of the image point I found isdetermined by the diameter of a single conducting fiber 52. In my imageconductor I assembled a bundle of such fibers which form a mosaiclikeend-face and which therefore can conduct a plurality of image points.All these image points will reproduce at the other end-face of the imageconductor the original image provided that the image conducting fibersremain in their original spatial relationship. Each fiber 52 shouldhave, as was explained above, a diameter corresponding to the size ofone image point. The diameter of 0.1 millimeter is well suitable for thepurposes of my invention. In order to conduct an image of an area, e.g.of one square centimeter We must have many fibers 52, the number offibers being dependent on the resolution of reproduced image that wedesire. If the resolution of the conducted image should be 4 lines permillimeter, and if the image is of one square centimeter in size, wewill need 40 fibers of 0.25 millimeter in diameter. As in manyexaminations it is not practical to be limited to the tield of 1 om?, Ipreferably use a few hundred of such fibers combined in one imageconductor, which will allow it to transmit an image of a large area.

The light conducting fibers should be polished on their external surfacevery exactly. They may be also preferably coated with a very thin lightopaque layer which should have a lower index of refraction than thelight conducting fiber itself. Such coating may have a thickness of onlya few microns. I found a great improvement of flexibility of the lightconductor 5I can be obtained by having the light conducting bers 52glued together only at their endfaces 51a and 51h. This is a veryimportant feature of my device because the main requirement from thelight conductor 51 is its iiexibility and malleability. If the fibers 52are glued together along their entire length the flexibility andmalleability is so much reduced that it may be not possible to use it inmany examinations in which the walls or passages are fragile and may bedamaged by a rigid instrument. I found unexpectedly that having theconducting fibers 52 free along their path between the end-faces willnot cause any deterioration of the conducted image. I found that inspite of the fact that fibers between their end surfaces were freelymovable there was no blurring of the conducted image. It must beunderstood however that the fibers 52 at both end-faces of the conductor51 must rigidly maintain their spatial relationship. Another importantfeature of this construction is that the diameter of the light conductor51 can be now increased because no space consuming binder or glue ispresent between the fibers 52 except at their endfaces. Instead of usingthe binder at the end-faces of fibers 52, they may also be held togetherat their endfaces by a fine mesh screen. Each ber is threaded throughone opening of said mesh screen and is held by said screen in constantposition.

It may be added that smaller losses of light may be obtained if thefibers 52 are hollow inside instead of being solid. An improvement incontrast of conducted images can be obtained by coating light conductingfibers 52 with an opaque material which eliminates the leakage of lightfrom one fiber to the adjacent one.

The number of fibers that can be used in many examinations will belimited by the diameter of the passages through which my intrascope hasto pass. As in many situations the channel may be only 1-2 cm. wide itwill be impossible to use a great number of fibers. I succeeded inovercoming this limitation, by using in combination the light conductor5l with a demagnifying optical system 53. By the use of the demagnifyingoptical system I can reduce the examined field to the diameter of theimage conductor fil. If the optical system `will demagnify the imagelive times, I can examine a field having 25 cm.2 with the imageconductor having the diameter of only 1 cm?. This combination representsa very important feature of my invention as it is not always practicalor feasible to limit the examined field only to the diameter of theimage conductor. Another important feature of my optical system 53 isthat it allows projection of the image on the end-face 5ta of the lightimage conductor through which it can be transmitted to the other end ofthe conductor. If the image were projected on the side of the conductor51 instead of on its end-face, it would not be conducted at all. This isaccomplished by means of the gable prism 53m.

The light image conductor 5I may be introduced into an examined partsimultaneously with the intrascope. In some cases it is preferable tointroduce my intrascope first and then insert the image conductor 51 or70 into intrascope. In some cases the gable prism 53a or the wholeoptical system 53 may be attached to the end-face 51a of the imageconductor to make one unit. The novel intrascope 5t) may have the sameconstruction of other parts as was explained above and illustrated inFIGURES l, la, and lb.

FIGURE 2 shows the novel intrascope which comprises my novel imageconductor system. The end-face 51a serves to receive the image. As wasexplained above the image is projected on the end-face 5in by theoptical system 53 and is at the same time demagniied to reduce the sizeof the image to the size of the cross-section of the image conductor Si.The image is conducted by the multiple flexible fibers 52. which formthe image conductor to the end-face 51h. The image emerging from theend-face Slb is projected by the optical system 54 on the televisionpick-up tube 55. If necessary the optical system 5d may be of themagnifying type to enlarge the previously demagniied image of theexamined part. The television pick-up tube 55 may be of the novel typedescribed and illustrated in FIG- URES l, la and lb. It should beunderstood however that all types of television pick-up tubes can beused in my intrascope in combination with image conductor 51. Thetelevision pick-up tube may be of the conventional vacuum tube type. Thetelevision pick-up tube may be of photo-emissive type, photoconductivetype, or photovoltaic type. The television pick-up tube may be ofvelocity modulation type. The television pick-up tube may use fast orslow scanning electron beam. The novelty of the combination of my imageconductor with my television pick-up system resides in the ability ofthe intrascope provided with this combination to penetrate intolocations which were inaccessible to my television pick-up system and totransmit said image from said inaccessible locations to the televisionpick-up tube. The television pickup tube can then transmit the image tothe outside of the examined part by means of coaxial cables and it cando it regardless of the distance between the television tube and theoutside. The image conductor on the other hand is limited in the abilityto conduct an image to the length of about l5 cm. because of prohibitivelosses of light. Therefore the combination of the image conductor with atelevision tube represents an important improvement in the art ofexamining recesses inaccessible to direct visualization. or toconventional optical systems. It should be understood that -my systemwill be also capable of producing color images. For this purpose therevolving color wheel 56a may be provided in front of the televisioncamera 55. Instead of the color wheel an optical system may be providedwhich splits the image into two or three color images and projects saidimages on different parts aat-asas 'i i of the photocathode. It shouldbe understood therefore that my invention may use all types oftelevision pick-up tubes which can produce color images.

I found that the image conductor 51 causes severe losses of light. Thisloss of light is dependent of the length of the image conductor, on thenumber of bends and the angle of said bends to which the image conductoris subject in its passage to the examined part. I found that losses oflight become prohibitive when the length of the conductor is about l cm.In some examinations the telcvision pick-up tube cannot be activatedwith the amount of light available after the passage through the imageconductor, because the optical system 5d disposed between the imageconductor and the television pick-up tube causes an additional loss of95% of useful light. in such cases I use the embodiment of my inventionshown in FIG 2a or 2b. ln this modification of my invention the imageconductor extends through the wall 55a of the pick-up tube 55 inside ofthe tube. The photoelectric photocathode 56 is now deposited on theend-face Sllb of the image conductor. The photocathode 56 may be ofthephotoemissive type as shown in FGURE 2a or photoconductive type as shownin FIGURE 2b. In this construction the loss of light caused by theoptical system 5d is completely eliminated which represents atwenty-fold increase in light available for the television pick-up tubeand which makes the television pick-up tube now responsive to the image.The image conductor is cemented to the end wall 55a of the tube 55 bythe vacuum type seal. In some cases it may be preferable to provide asupport for the light image conductor near the face 55a of thetelevisie-n tube to reduce the pull of the image conductor 5ft againstthe wall of the pick-up tube.

Another modification of my intrascope is shown in FIGURE 3a. In thisembodiment of the invention the image conductor Sil has its end-face 51aadjacent to the distal end of the intrascope. The window 9i can beopened by mechanical means which are well known in the art `and theend-face Sla of the image conductor 51 may be brought slightly forward.This will result in apposition of the image conductor with the examinedpart. in this ernbodiment of the invention the light source forillumination of the examined part may be provided at the proximal endSIb of the image conductor. The light source 7a projects the light ontomirror which has the property of partly reflecting and partlytransmitting the light. Such mirrors are well known in the art and it isbelieved therefore that their detailed description is not necessary. Thelight reilected by the mirror 53 is conducted by the image conductor 5lto the examined part and forms an image thereof. This light is reflectednext by the examined part and returns again through the image conductor5l to the outside. As the mirror 53 is half-redecting andhalf-transparent the image of the examined part can pass through themirror 5S and be focused by the optical system on the photocathode ofthe television pick-up tube.

Another preferred embodiment of my invention is shown in FIGURE 3. Theintrascope in this modification consists of a rigid part, flexible part2a and semi-flexible tip 3. The mechanical construction of these partsis the same as described above and does not have to be repeated. Theinternal image producing and transmitting structures of the flexiblepart 2o are completely different. In particular the illuminating system7 is replaced in this modification by the flying spot kine-scope. Theminiature flying spot kinescope oa or '76 was shown in FGURE l and is avacuum tube provided with an electron gun ZS producing a ne beam ofelectrons Z9, with circuits 3fm and for deliecting said electron beam intwo mutually perpendicular directions and also having a scrccnS-llcoatcd with a fluorescent material. The electron gun consists of anelectron emission source and an electron-optical system to focus theelectrons into a fine beam. The fluorescent screen of the kinescope mustbe of a phosphor of a very short persistence in order to obtain a goodresolution of image. ZnO phosphor has decay time of one microsecond andis suitable therefore for this purpose. Still better results will beobtained by applying ZnS phosphor and utilizing only the ultra-violetcomponent of its fluorescent emission, which has the decay time of l/lmicrosecond. The electron beam of the kinescope has toscan thefluorescent screen in a predetermined pattern. This scanning motion ofthe electron beam is obtained by the electro-static or magetic fiel-:lsS-Jrz or Etib, which produce deflection of said beam. rThis scanningelectron beam 23 produces a scanning light spot which illuminates theexamined part through window l2 and produces successive image points ofsaid exa-mined part. Successive image points are admitted through windowI8 into intrascope and are projected by the optical system i5 on theend-face of the image conductor 77. The image conductor 77 in thismodification of my invention consists of a single rod of material, whichis flexible and has a high index of refraction, such as Lucite, acrylicplastics, poly-styrenes or other materials. As was explained above, suchmaterials cannot conduct an image. They can conduct a light signal only.In my novel device, the image s produced by a rapid succession of singleimage points. Each image point can be conducted by the conductor 77,because it represents only one signal. Each conducted image point, afterit emerges from the conductor 77, is projected on a single or pluralphoto-tubes or photocells and is converted thereby into an electricalsignal. If a black and white image is suffrcient, only one photo-tube 73has to be used. The phototube converts, as was explained above, eachlight image point into an electrical signal. The successive electricalsignals are conducted by flexible coaxial cables 31 to the outside ofthe intrascope and of the examined part. These transmitted electricalsignals are next fed into appropriatereceivers, such as kinescopes,facsimile receivers or skiatrons, known also as a dark trace tube, andare reconverted into a visible image for inspection or lor photographicrecording. In case a color image of the examined part is necessary, wemay use two or three phototubes or photocells. The phototube 73a willserve to receive red image points; phototube 78b will serve to receivegreen image points, and phototube 78C will receive blue image points. Awhite light image point may be split into its component colors by theuse of a suitable optical system. Dichroic mirrors titl are useful forthis purpose. It should be understood, however, that there are manyoptical means that can be used instead of said dichoic mirrors. In somecases, it is preferable to use, instead of dichoic mirrors, the rotatingcolor disc 53a. The importance of this construction lies in the factthat I may use now one phototube or one photocell instead of threephototubcs, which will markedly reduce the size of the intrascope. Inthis modification, the speed of the flying spot produced by thelnnescope '76 has to be increased so that the whole examined area may beilluminated during the time in which one of three color filters of thedisc S6 is in front of the single phototube 7S. The rotating color wheelSe may he sct in motion by a miniature motor, such as used in electricwrist watches, and which may be disposed within the intrascope. In sucha case, the color wheel may be mounted on the shaft of said motor. Insome cases it is preferable to have the motor disposed outside of theexamined part. In such event, the motor may be connected with therotating disc 56 by means of flexible cables or the power muy betransmitted from the motor to the disc by pneumatic means or hydraulicmeans. The pressure exerted by the motor or a column of air or liuid ispropagated by said pneumatic or hydraulic means to the disc and willcause its rotation.

The reproduction of color images may be improved by having in front ofeach phototube or photocell 78a, 7311 and 78e, suitable filters 79a, 7%and 79C, which transmit only red, green and blue light respectively.

It should be understood that all types of phototubes or photocells maybe used for purposes of my invention. In particular I may use phototubesof photoemissive type, of photo-conductive type or photovoltaic type.The photocells having silicon, germanium or bismuth in combination withantimony or aluminum with antimony are most suitable because suchphotocells show high frequency response, which is necessary for theoperation of my device. Also modified photo-transistors, which have alarge photo-sensitive surface in contradistinction to the conventionalones, in which the photo-sensitive area is very small, may be used in myinvention.

It may be added that when dealing with short distances, which do notcause a prohibitive loss of light, the light conductor 77 may extend tothe outside of the examined part and the image then may be examineddirectly without the need of conversion of light image points intoelectrical signals, as was explained above and illustrated in FIG- URE3. In such cases the image points which appear successively at theend-face 77b of the light conductor 77, may be projected by an opticallens and may be seen by the examiner directly because, due to thepersistance of vision, the successive image points conducted by theconductor 77 will reproduce a total image in the retina of the examiner.

In some cases the light conductor 77 does not have to extend to theoutside of the examined part, but it may be used in combination with anoptical system, which will deliver the light image from the end-face 77bof the conductor to the outside of the examined part. This arrangementis feasible only in locations in which the course of the examinedpassages between the end-face 77b of the conductor and the outside iswell known in advance, so that a suitable optical system can beprovided.

In some applications where the distance between the examined part andthe outside is small, also the image conductor which consists ofplurality of fibers conducting light may be used without a televisionsystem. This ernbodiment of my invention is shown in FIGURE 4. The lightimage produced by the light source 7 is conducted by the image conductor70 to the outside where it can be examined visually, recorded orphotographed. In some cases the light conductor 70 does not have toextend to the outside of the examined part because the course of theexamined part becomes straight. In this event it is preferable tocombine the light image conductor with an additional optical systemwhich will project the image from the intrascope to the outside of theexamined part.

Another embodiment of 4my invention is shown in FIGURE 5 in which thelight source is disposed outside of the examined part and is projectedonto the end-face of the image conductor 70 by the halfreflecting andhalftransparent mirror 53, as was explained above.

The light image of the examined part which is transmitted by the imageconductor 70 to the outside in some cases may be too weak for visualinspection and may require dark adaptation of the eyes. In such casesthe image will be also too weak for photographing. For such examinationsI made a modification of my invention which is shown in FIGURE 6. Inthis embodiment of my invention the image conductor 70 is inserted intovacuum tube 60 through its wall 60a. The photocathode 61 of the vacuumtube which may be of photoemissive type or photoconductive type isdeposited on the end-face 51b of the image conductor. The light emergingfrom the end-face 51b can now excite the photocathode 61 as the opticalsystem is eliminated, which as was explained is causing a prohibitiveloss of light. The electrons emitted from the photocathode 61 are imagedby magnetic or electrostatic lenses 64 and are focused on thefluorescent screen 62 disposed at the otherend of the tube and protectedby the light-reflecting layer 62a such as of aluminum. The electronimage may be also intensified by accelerating fields 64. Furthermore itmay be intensified by electron-optical diminution which results in anincrease in intensity proportional to the square power of lineardemagnication.

This may be accomplished by means of electromagnetic 63 or electrostaticlenses 64. The electrostatic lenses may be in the form of series ofcylinders or rings of progressively smaller diameter. They are disposedinside of the tube and are connected to an outside source of potential.The magnetic or electromagnetic lenses may be in the form of coilssurrounding the tube from outside. Such coils may be tapered or may bein the form of a short coil extending from some point between thephotocathode 61 and the iiuoroscent screen 62, up to said tluoroscentscreen 62. The intensified image which appears on the fiuorescent screencan be inspected visually by the observer directly or may be firstmagnified by an optical eyepiece 64u. The optical magnification of theelectronoptically diminished image does not result in its loss ofbrightness as long as said magnification does not exceed certain limits.In this way the intensification of the image obtained by means ofelectron-optical diminution is not lost although the image is magnifiedagain optically. Therefore the image of the examined part which was tooweak for examination can now be presented with necessary brightness.

The use of the image tube 6ft may also be necessary when using as imageforming radiation invisible radiation such as ultra-violet or infrared.In cases in which the preservation of light is not critical it may bepossible to project the image emerging from end-face `Slb of the imageconductor 70 on the photocathode 61 of the image tube by optical means.In cases in which the definition of the reproduced image is notimportant, the end-face 51b of the image conductor 70 may -be attachedto the endface of the image tube to be in tight apposition to theexternal surface of the image tube 60. The thickness of the wall of theimage tube 60 which separates the end face 51b of the image conductorfrom the photocathode 61 will cause however a marked blurring of theimage. The image tube may be also advantageously used within theintrascope in order to intensify the Weak image emerging from theend-face of the image conductor before it is projected on the televisionpick-up tube. In this embodiment the image tube has to be of miniaturesize. This can be accomplished by eliminating focusing electrodes andbringing the photocathode 61 very close to the fluorescent imagereproducing screen 62 to prevent blurring of the electron image.

In some cases it is preferable to use as the light 7a or 65 forillumination of the examined part a polarized light. The image conductedby the image conductor to the observer is not polarized any more due tomultiple reflections. Therefore by providing means which will stop thepolarized light from reaching the observer but will transmit thenon-polarized light, the contrast of the examined part will be markedlyimproved. This construction is of critical importance, in devices inwhich the light `for illumination of the examined part has to bedelivered to the examined part by the sameV image conductor which servesto return the image to the observer. There are many ways in the art toeliminate the polarized light. FIGURE 5 shows one of the means suitablefor the purpose of this invention. The rotating prism 59 serves to stopthe polarized light from the source 65 and it will at the same timetransmit the non-polarized light. The resulting improvement in contrastwill make my device operative in many cases in which without thisimprovement it would not be feasible to examine the received image.

It should be clearly understood that all my intrascopes can serve andproduce and transmit color images as Well.

It is also to be understood that in some applications the encasing meansfor the image conductor or for pick-up tubes may be omitted.

My invention is not limited to visible light images. All my intrascopesmay be made responsive to invisible assignee images on either side ofvisible spectrum by using an appropriate photo-sensitive layer in thephotocathode of the television pick-up tube. 1t is to be understood thatall my intrascopes may serve for receiving images formed not only byvarious eiectromagnetic radiations such as ultra-violet, infra-red,etc., but also by particle radiation such as neutrons, alphaparticles,protons, electrons or by ions. In such cases the photocathode of thepick-up tube described above may be provided with an atomic particlesensitive phosphor on the side facing said image, or may have a specialelectron or other atomic particle emissive photocathode.

The embodiment of my invention illustrated in FIF- URE 5 may be alsomodified by using instead of the image conductor 7i), which consists ofplural bers 52, the conductor 77, which consists of one solid rod ofmaterial conducting light, as was explained above. In order to make thismodification operative, I found that the source of light must be able toproduce a scanning light illumination. Therefore, instead of theelectrical bulb 65 I use in this embodiment of my invention the flyingspot of light produced by a vacuum tube 16a or 76, as was describedabove. The remaining parts of my device may be the same as shown inFIGURE 5.

I also found that the novel image conductors 51, '70 or 77 may transmitnot only white light Ibut also infrared light and ultra-violet light. Itis to be understood therefore that the term light as used in mydisclosure embraces the visible light as well as the invisible.

Another important discovery was that supersonic waves can be alsoconducted by the conductors 51, 7d or 77. By using as a source of imageforming radiation piezoelectric or magnetostrictive means, we mayproduce supersonic images of the examined part. Piezoelectric means maybe in the form of oscillating crystals of quartz, titanate compounds,Rochelle salts and other similar materials.

As various possible embodiments might be made of' the above invention,and as yvarious changes might be made in the embodiment above set forth,it is to be understood that all matter herein set forth or shown in theaccompanying drawings is to -be interpreted as illustrative and not in alimiting sense.

I claim:

1. An inspection device comprising in combination an elongated tubularhousing adapted in size and shape for being introduced into an examinedpart, a source of light for illumination of said examined part, a windowin said housing for admitting an image of the examined area, opticalmeans for producing the image of said examined area, a bundie offlexible members comprising a plurality of members operating by internalreiiection of light, said members being disposed in said housing forreceiving and transporting said image, each of said plurality of membershaving a lcore of a light transparent material having a high index ofrefraction and each of said plurality of members covered by coatingmeans of a lower index of refraction than said core secured thereto,said coating means having a thickness not exceeding a few microns, forpreventing escape of light from one of said members to another,essentially all said members having a diameter of a fraction of onemillimeter, said members furthermore being assembled to provide anendface of an appreciable crosssection, said bundle comprising inaddition means for maintaining said members at each end-face of saidbundle in a fixed spatial relationship to each other, said maintainingmeans being mounted only at the ends of said bundle and saidillumination being conducted to said examined part by a plurality ofiiexible tibers operating by internal reflection of light and having acore of a high index of refraction and coating means of a lower index ofrefraction than said core.

2. A device as defined in claim 1, in which said coating means are lightopaque.

3. A device as dened in claim 1, in which said endiiace of said bundleis mounted opposite said window and directed toward said window.

4. A device as defined in claim 1, in which said endface of said bundleis mounted coaxially with said window.

5. A device as defined in claim 1, in which said bundle transmits imagesproduced by invisible light.

6. A device as defined in claim 1, in which said maintaining meanscomprise a binder.

7. A device as dened in claim 1, which comprises in additionphotosensitive means for receiving said image transported by saidbundle.

An inspection device comprising in combination an elongated tubularhousing adapted in size and shape for being introduced into an examinedpart, a window mounted in the distal wail of saidhousing for receivingan image, optical means for producing said image of an examined area, abundle of tiexible members comprising a plurality of members operatingby internal reflection of light, said members being disposed in saidhousing and having one end-face mounted opposite said window anddirected toward said window for receiving and transporting said image,each of said plurality of members having a core of light transparentmaterial having a high index of refraction and each of said plurality ofmembers covered `by coating means of a lower index of retraction thansaid core secured thereto, said coating means having thickness notexceeding a few microns for preventing escape of light from one of saidmembers to another, essentially all said members having a diameter of afrac-tion of one millimeter, said members being assembled to provide anend-face of an appreciable crosssection, said bundle comprising inaddition means for maintaining said -members at each end-face of saidbundle in a fixed spatial relationship to each other, said maintainingmeans being mounted only at the ends of said bundle.

9. A device as defined in claim 8, in which said endface ot said bundleis mounted coaxially with said window.

1t). A device as defined in claim 8, in which said coating means arelight opaque.

11. A device as defined in claim 8, in which illumination is conductedto said examined part by a plurality of tiexible fibers operating byinternal reflection of light and having a core of a high index ofrefraction and coating means of a lower index of refraction than saidcore.

12. A device as dened in claim S, in which lsaid bundle transmits imagesproduced by invisible light.

13. A device as defined in claim 8, which comprises in additionphotosensitive means for receiving said transported image.

References Cited UNiTED STATES PATENTS 1,751,584 3/1930 Hansell 250-227X 2,877,368 3/1959 Sheldon. 3,021,834 2/1962 Sheldon 88-1 OTHERREFERENCES A. C. S. van Heel: A New Method of Transporting OpticalImages Without Aberratio-ns, in Nature, 173 (4392), p. 39, Jan. 2, 1954.

H. H. Hopkins et al.: A Flexible Fibrescope, Using Static Scanning, inNature, 173 (4392), pp. 39-41, Jan. 2, 1954.

RALPH G. NILSON, Primary Examiner.

M. A. LEAVITI, Assistant Examiner.

1. AN INSPECTION DEVICE COMPRISING IN COMBINATION AN ELONGATED TUBULARHOUSING ADAPTED IN SIZE AND SHAPE FOR BEING INTRODUCED INTO AN EXAMINEDPART, A SOURCE OF LIGHT FOR ILLUMINATION OF SAID EXAMINED PART, A WINDOWIN SAID HOUSING FOR ADMITTING AN IMAGE OF THE EXAMINED AREA, OPTICALMEANS FOR PRODUCING THE IMAGE OF SAID EXAMINED AREA, A BUNDLE OFFLEXIBLE MEMBERS COMPRISING A PLURALITY OF MEMBERS OPERATING BY INTERNALREFLECTION OF LIGHT, SAID MEMBERS BEING DISPOSED IN SAID HOUSING FORRECEIVING AND TRANSPORTING SAID IMAGE, EACH OF SAID PLURALITY OF MEMBERSHAVING A CORE OF A LIGHT TRANSPARENT MATERIAL HAVING A HIGH INDEX OFREFRACTION AND EACH OF SAID PLURALITY OF MEMBERS COVERED BY COATINGMEANS OF A LOWER INDEX OF REFRACTION THAN SAID CORE SECURED THERETO,SAID COATING MEANS HAVING A THICKNESS NOT EXCEEDING A FEW MICRONS, FORPREVENTING ESCAPE OF LIGHT FROM ONE OF SAID MEMBERS TO ANOTHER,ESSENTIALLY ALL SAID MEMBERS HAVING A DIAMETER OF A FRACTION OF ONEMILLIMETER, SAID MEMBERS FURTHERMORE BEING ASSEMBLED TO PROVIDE ANENDFACE OF AN APPRECIABLE CROSSSECTION, SAID BUNDLE COMPRISING INADDITION MEANS FOR MAINTAINING SAID MEMBERS AT EACH END-FACE OF SAIDBUNDLE IN A FIXED SPATIAL RELATIONSHIP TO EACH OTHER, SAID MAINTAININGMEANS BEING MOUNTED ONLY AT THE ENDS OF SAID BUNDLLE AND SAIDILLUMINATION BEING CONDUCTED TO SAID EXAMINED PART BY A PLURALITY OFFLEXIBLE FIBERS OPERATING BY INTERNAL REFLECTION OF LIGHT AND HAVING ACORE OF A HIGH INDEX OF REFRACTION AND COATING MEANS OF A LOWER INDEX OFREFRACTION THAN SAID CORE.